Wedge antenna system for sector operation



Oct. 11, 1955 J. J. NAIL ET'AL 2,720,590

WEDGE ANTENNA SYSTEM FOR SECTOR OPERATION Filed Sept. 8, 1953 INVENTORS JAMES d. NAIL w/u/AM M. SPA/V08 BY ATTORN EY United States Patent ice i.

WEDGE ANTENNA SYSTEM FOR SECTOR OPERATION Application September 8, 1953, Serial No. 378,752

7 Claims. (Cl. 25033.65)

. This invention relates generally to. an antenna system for ultra high frequency radiationland; more particularly, to antenna systems employing reflectors for projection of the radiation in a desired direction.

For certain applications where omnidirectional coverage is required but cannot, for various reasons, be obtained with a single omnidirectional radiator, sector operation of antennas must be employed. This is accomplished by providing an array of antennas each having a radiation pattern which covers only one sector of the region of interest. To simplify operational problems and reduce cost, it is extremely desirable to reduce the number of sectors and thus keep the number of antennas to a minimum. Obviously, two antennas each covering a sector of 180 is the minimum number of sector antennas that can be utilized to provide omnidirectional coverage.

Sector coverage in general imposes severe requirements on the individual antennas if eflicient operation is to be realized. In particular, a special type of directional radiator is required having its radiation pattern in one plane capable of being controlled over a wide angular range so that the sector coverage may be varied between a very narrow angle up to 180. The radiation pattern of the sector antenna must cut ofi as rapidlly as possible for any particular sector coverage so that in all cases the region of radiation pattern overlap between neighboring antennas is minimized. The radiation pattern characteristic of the sector antenna must remain substantially constant over wide frequency bands and the impedance characteristic of the antenna must be such that it can be matched to a transmission line over wide frequency bands.

One of the objects of this invention, therefore, is to provide an antenna particularly adapted for sector operation in accordance with the above-mentioned desirable essential characteristics.

Another object of this invention is to provide an antenna having a broad controlled radiation pattern in the plane orthogonal to the plane of polarization over a broad band of frequencies.

A further object of this invention is to provide an antenna adapted for sector operation which substantially is insensitive to metallic surfaces directly behind it.

In accordance with a feature of this invention it is proposed to provide a wedge shaped reflector rearward of a dipole antenna to provide a broad response pattern in a plane orthogonal to the plane of polarization. By varying the dimensions of the wedge shaped reflector the radiation pattern of the sector antenna of this invention may be controlled.

The above-mentioned and other features and objects of this invention will become more apparent by reference to the following description taken in conjunction with the accompanying drawings, in which:

The figure of the drawing is a perspective view of a wedge antenna for sector operation in accordance with the principles of this invention.

A 2,720,590 Patented -Oct.- 11, 1955 Referring to the figure of the drawing the reference character 1 indicates a wedge shaped reflector having mounted thereon at the apex of its excluded angle an: tenna structure -2. The antenna structure 2 is connected to energizing or signal transducer'means (not shown) by a transmission line 3. i 2

The antenna structure 2 comprises adipole radiator located a distance D in front of the metallic reflector; 1. The metallic'reflector 1 is in the shape of a wedge having an included angle 0, a side width A'and side length B. The parameters of the antenna system are. dependent upon the frequency 'of operation, the' frequency band to be covered, the impedance presentedto: the transmis sion line, the desired H'zplane half pow'enwidth and the required amount of shielding 'from'metallic 'objects: to. the rear of the reflector 1.' In general a satisfactory range'of parameters wouldbe asfo'llowsx 1.

A=from l to 2 wavelengths B=from to 1 wavelength D=from to wavelength 0=from 30 to 180 degrees As the included angle 0 decreases, maintaining D; A and B constant, the H-plane half-power width in degrees increases. For a lesser distance D between the radiator 1 and the reflector 2, 0 must be decreased to maintain the same H-plane half-power points or in other words as D is made smaller 0 must be decreased to obtain the same H-plane half-power width. Thus, in general, for coverage of large frequency bands the angle 0 is smaller since the distance D should not exceed of a wavelength.

Varying the reflector side length B within the indicated range does not noticeably affect the H-plane pattern but when the side width A is selected between A and l wavelength the back lobe of the radiation pattern is increased otherwise leaving the H-plane pattern unaflected. When A is selected greater than one wavelength some variation does occur in the H-plane pattern.

One antenna system in accordance with the principles of this invention for operation at a 1.75:1 frequency band ratio utilized a wedge reflector having a side width A and side width B each of 40 inches or one wavelength at the midfrequency. The distance D from the reflector to the radiator was 12 inches or 0.3 of a Wavelength at midfrequency. The included angle 0 was which yielded an I-I-plane power pattern of approximately between half-power points.

It is of course obvious that the individual antennas as described above consisting of a radiator and wedge reflector can be stacked in the plane of polarization to yield any desired amount of E-plane directivity.

It should also be pointed out that the Wedge reflector of this invention has little effect on the impedance of the radiator.

While we have described above the principles of our invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of our invention as set forth in the objects thereof and in the accompanying claims.

We claim:

1. A broad band sector antenna comprising a wedge shaped reflector of a given included angle having two surfaces, each of a given width and length, joined to form a leading edge, and a stationary dipole radiator located a given distance in front of said leading edge external to said included angle and parallel to said leading edge.

2. An antenna according to claim 1 wherein said given width is within the range of one-half to two wavelengths toone wavelength of the center operating frequency.

3. An antenna according to claim 1 wherein said given distance is within the range of one-eighth to three-eighths of a Wavelength of the center operating frequency.

4. A broad band sector antenna'comp'rising a stationary dipole radiator, a wedge shaped reflector, the leading edge apex of said reflector facing said radiator and parallel thereto said radiator disposed externally to the included angle of said wedge whereby said antenna has a substantially wide direction of maximum response.

5. A broad band plane polarize'dantenna comprising a wedge shaped reflector having two metallic surfaces joined at a leading edge to form a V, aistationary dipole radiator disposed in front of said leading edge externally to the included angle of said wedge and having its plane of polarization parallel to said leading edge, and a transmission line extending through said reflector for coupling to said radiator.

6. An antenna according to claim 5 wherein the included angle of said V is substantially less than 180.

7. A broad band plane polarized sector antenna comprising a wedge shaped reflector having two metallic surfaces each one wavelength square joined together at an angle of substantially 80 to form a leading edge of said wedge, a stationary dipole radiator disposed threetenths of a wavelength in front of and parallel to said leading edge and externally to said angle and a transmission line extending through an opening in said leading edge for coupling to said radiator.

References Cited in the file of this patent UNITED STATES PATENTS 2,270,314 Kraus Jan. 20, 1942 FOREIGN PATENTS 642,385 Germany July 7, 1937 OTHER REFERENCES Proceedings of I. R.v E., vol. 28, No. 11,- Novembe 20 1940, pages 513 to 519. 

